把一些價值從sqlite

我有一個問題與SQLite。我想從我的數據庫中的一些值（X，Y）（源碼）把一些價值從sqlite

這裏是我的代碼：

從結果ID和X

Cursor notesCursor = mDbHelper.fetchAllNotes(); 
     startManagingCursor(notesCursor);  

     double x, y ; 

     try { 
      x = notesCursor.getDouble(notesCursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_ROWID)); 
     } catch (NumberFormatException e) { 
      // TODO 
      return; 
     } 
     try { 
      y = notesCursor.getDouble(notesCursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_RESULT)); 
     } catch (NumberFormatException e) { 
      // TODO 
      return; 
     } 
     mCurrentSeries.add(x, y); 
     if (mChartView != null) { 
      mChartView.repaint(); 
     }

年。但它沒有奏效，我錯過了什麼？我真的需要幫助，感謝

之前，我已經改變了我這樣的代碼：

Cursor notesCursor = mDbHelper.fetchAllNotes(); 
     startManagingCursor(notesCursor);  
     double x, y; 

     try { 
      notesCursor.moveToFirst(); 
      x = notesCursor.getDouble(notesCursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_ROWID)); 
     } catch (NumberFormatException e) { 
      e.printStackTrace(); 
      return; 
     } 
     try { 
      notesCursor.moveToFirst();   
      y = notesCursor.getDouble(notesCursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_RESULT)); 
     } catch (NumberFormatException e) { 
      e.printStackTrace(); 
      return; 
     }

，但我仍然有錯誤，請幫我解決了這個問題，謝謝

我的日誌貓：

08-28 01:01:55.776: ERROR/AndroidRuntime(669): java.lang.RuntimeException: Unable to start activity ComponentInfo{org.achartengine.chartdemo.demo/org.achartengine.chartdemo.demo.XYChartBuilder}: java.lang.NullPointerException 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.os.Handler.dispatchMessage(Handler.java:99) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.os.Looper.loop(Looper.java:123) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.app.ActivityThread.main(ActivityThread.java:4627) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at java.lang.reflect.Method.invokeNative(Native Method) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at java.lang.reflect.Method.invoke(Method.java:521) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at dalvik.system.NativeStart.main(Native Method) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669): Caused by: java.lang.NullPointerException 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at org.achartengine.chartdemo.demo.XYChartBuilder.onCreate(XYChartBuilder.java:108) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
08-28 01:01:55.776: ERROR/AndroidRuntime(669):  ... 11 more

嗯，我又改變了我的代碼，像這樣：

Cursor notesCursor = mDbHelper.fetchAllNotes(); 
     if (notesCursor != null) { 
      startManagingCursor(notesCursor); 
     } else { 
      System.err.println("Cursor is null"); 
     } 


    double x, y; 

    try { 
     notesCursor.moveToFirst(); 
     x = notesCursor.getDouble(notesCursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_ROWID)); 
    } catch (NumberFormatException e) { 
     e.printStackTrace(); 
     return; 
    } 
    try { 
     y = notesCursor.getDouble(notesCursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_RESULT)); 
    } catch (NumberFormatException e) { 
     e.printStackTrace(); 
     return; 
    } 
    mCurrentSeries.add(x, y); 
    if (mChartView != null) { 
     mChartView.repaint(); 
    }

但它仍然沒有工作，我錯過了什麼？感謝您的幫助

完整代碼：

package chart.android.research; 

import java.io.File; 
import java.io.FileOutputStream; 

import org.achartengine.ChartFactory; 
import org.achartengine.GraphicalView; 
import org.achartengine.chart.PointStyle; 
import org.achartengine.chartdemo.demo.R; 
import org.achartengine.model.SeriesSelection; 
import org.achartengine.model.XYMultipleSeriesDataset; 
import org.achartengine.model.XYSeries; 
import org.achartengine.renderer.XYMultipleSeriesRenderer; 
import org.achartengine.renderer.XYSeriesRenderer; 
import org.achartengine.tools.PanListener; 
import org.achartengine.tools.ZoomEvent; 
import org.achartengine.tools.ZoomListener; 

import android.app.Activity; 
import android.database.Cursor; 
import android.graphics.Bitmap; 
import android.graphics.Bitmap.CompressFormat; 
import android.graphics.Color; 
import android.os.Bundle; 
import android.os.Environment; 
import android.view.View; 
import android.view.ViewGroup.LayoutParams; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.LinearLayout; 
import android.widget.Toast; 

public class XYChart extends Activity { 
    public static final String TYPE = "type"; 

    private XYMultipleSeriesDataset mDataset = new XYMultipleSeriesDataset(); 

    private XYMultipleSeriesRenderer mRenderer = new XYMultipleSeriesRenderer(); 

    private XYSeries mCurrentSeries; 

    private XYSeriesRenderer mCurrentRenderer; 

    private String mDateFormat; 

    private Button mAdd; 

    private EditText mX; 

    private EditText mY; 

    private GraphicalView mChartView; 

    private int index = 0; 

    private NotesDbAdapter mDbHelper; 

    @Override 
    protected void onRestoreInstanceState(Bundle savedState) { 
    super.onRestoreInstanceState(savedState); 
    mDataset = (XYMultipleSeriesDataset) savedState.getSerializable("dataset"); 
    mRenderer = (XYMultipleSeriesRenderer) savedState.getSerializable("renderer"); 
    mCurrentSeries = (XYSeries) savedState.getSerializable("current_series"); 
    mCurrentRenderer = (XYSeriesRenderer) savedState.getSerializable("current_renderer"); 
    mDateFormat = savedState.getString("date_format"); 
    } 

    @Override 
    protected void onSaveInstanceState(Bundle outState) { 
    super.onSaveInstanceState(outState); 
    outState.putSerializable("dataset", mDataset); 
    outState.putSerializable("renderer", mRenderer); 
    outState.putSerializable("current_series", mCurrentSeries); 
    outState.putSerializable("current_renderer", mCurrentRenderer); 
    outState.putString("date_format", mDateFormat); 
    } 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.xy_chart); 
    mX = (EditText) findViewById(R.id.xValue); 
    mY = (EditText) findViewById(R.id.yValue); 
    mRenderer.setApplyBackgroundColor(true); 
    mRenderer.setBackgroundColor(Color.argb(100, 50, 50, 50)); 
    mRenderer.setAxisTitleTextSize(16); 
    mRenderer.setChartTitleTextSize(20); 
    mRenderer.setLabelsTextSize(15); 
    mRenderer.setLegendTextSize(15); 
    mRenderer.setMargins(new int[] { 20, 30, 15, 0 }); 
    mRenderer.setZoomButtonsVisible(true); 
    mRenderer.setPointSize(10); 

    mAdd = (Button) findViewById(R.id.add); 
     XYSeries series = new XYSeries("Kenaikan Gula Darah"); 
     mDataset.addSeries(series); 
     mCurrentSeries = series; 
     XYSeriesRenderer renderer = new XYSeriesRenderer(); 
     mRenderer.addSeriesRenderer(renderer); 
     renderer.setPointStyle(PointStyle.CIRCLE); 
     renderer.setFillPoints(true); 
     mCurrentRenderer = renderer; 
     setSeriesEnabled(true); 

     Cursor notesCursor = mDbHelper.fetchAllNotes(); 
     if (notesCursor != null) { 
      startManagingCursor(notesCursor); 
     } else { 
      System.err.println("Cursor is null"); 
     }  
     double x, y; 

     try { 
      notesCursor.moveToFirst(); 
      x = notesCursor.getDouble(notesCursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_ROWID)); 
     } catch (NumberFormatException e) { 
      e.printStackTrace(); 
      return; 
     } 
     try { 
      y = notesCursor.getDouble(notesCursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_RESULT)); 
     } catch (NumberFormatException e) { 
      e.printStackTrace(); 
      return; 
     } 
     mCurrentSeries.add(x, y); 
     if (mChartView != null) { 
      mChartView.repaint(); 
     } 

    } 

    @Override 
    protected void onResume() { 
    super.onResume(); 
    if (mChartView == null) { 
     LinearLayout layout = (LinearLayout) findViewById(R.id.chart); 
     mChartView = ChartFactory.getLineChartView(this, mDataset, mRenderer); 
     mRenderer.setClickEnabled(true); 
     mRenderer.setSelectableBuffer(100); 
     mChartView.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      SeriesSelection seriesSelection = mChartView.getCurrentSeriesAndPoint(); 
      double[] xy = mChartView.toRealPoint(0); 
      if (seriesSelection == null) { 
      Toast.makeText(XYChartBuilder.this, "No chart element was clicked", Toast.LENGTH_SHORT) 
       .show(); 
      } else { 
      Toast.makeText(
       XYChartBuilder.this, 
       "Chart element in series index " + seriesSelection.getSeriesIndex() 
        + " data point index " + seriesSelection.getPointIndex() + " was clicked" 
        + " closest point value X=" + seriesSelection.getXValue() + ", Y=" + seriesSelection.getValue() 
        + " clicked point value X=" + (float) xy[0] + ", Y=" + (float) xy[1], Toast.LENGTH_SHORT).show(); 
      } 
     } 
     }); 
     mChartView.setOnLongClickListener(new View.OnLongClickListener() { 
     @Override 
     public boolean onLongClick(View v) { 
      SeriesSelection seriesSelection = mChartView.getCurrentSeriesAndPoint(); 
      if (seriesSelection == null) { 
      Toast.makeText(XYChartBuilder.this, "No chart element was long pressed", 
       Toast.LENGTH_SHORT); 
      return false; // no chart element was long pressed, so let something 
      // else handle the event 
      } else { 
      Toast.makeText(XYChartBuilder.this, "Chart element in series index " 
       + seriesSelection.getSeriesIndex() + " data point index " 
       + seriesSelection.getPointIndex() + " was long pressed", Toast.LENGTH_SHORT); 
      return true; // the element was long pressed - the event has been 
      // handled 
      } 
     } 
     }); 
     mChartView.addZoomListener(new ZoomListener() { 
     public void zoomApplied(ZoomEvent e) { 
      String type = "out"; 
      if (e.isZoomIn()) { 
      type = "in"; 
      } 
      System.out.println("Zoom " + type + " rate " + e.getZoomRate()); 
     } 

     public void zoomReset() { 
      System.out.println("Reset"); 
     } 
     }, true, true); 
     mChartView.addPanListener(new PanListener() { 
     public void panApplied() { 
      System.out.println("New X range=[" + mRenderer.getXAxisMin() + ", " + mRenderer.getXAxisMax() 
       + "], Y range=[" + mRenderer.getYAxisMax() + ", " + mRenderer.getYAxisMax() + "]"); 
     } 
     }); 
     layout.addView(mChartView, new LayoutParams(LayoutParams.FILL_PARENT, 
      LayoutParams.FILL_PARENT)); 
     boolean enabled = mDataset.getSeriesCount() > 0; 
     setSeriesEnabled(enabled); 
    } else { 
     mChartView.repaint(); 
    } 
    } 

    private void setSeriesEnabled(boolean enabled) { 
    mX.setEnabled(enabled); 
    mY.setEnabled(enabled); 
    mAdd.setEnabled(enabled); 
    } 
}

來源

2011-08-27 Handy

你得到任何價值了光標之前錯過moveToFirst()方法。 add e.printStackTrace（）;到所有的catch塊（而不是TODO），你會看到真正的原因。

順便提一下，不推薦使用startManagingCursor（）方法。

好了，試試這個現在改變此密碼

Cursor notesCursor = mDbHelper.fetchAllNotes(); 
startManagingCursor(notesCursor);

到光標notesCursor = mDbHelper.fetchAllNotes（）;

if (notesCursor != null) { 
    startManagingCursor(notesCursor); 
} else { 
    System.err.println("Cursor is null"); 
}

並確保mDbHelper也不爲空。

來源

2011-08-27 14:57:23 bitle

ehm，你能告訴我從我的代碼中的例子嗎？我有點困惑與movetofirst方法，我從來沒有使用過，謝謝 – Handy

再次檢查我的答案。另外，刪除第二個moveToFirst（）; – bitle

它仍然沒有工作，我已經包括我的最新代碼在我的問題，我錯過了什麼？謝謝 – Handy

把一些價值從sqlite

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